Teaching systems in which students are provided questions on a screen and are asked to provide answers through a keyboard are well-known in the art. In one such system, disclosed by J. Laplume in German Patent Application 1964702, each successive frame of a paper band moved past a viewing window contains a printed question posed to an individual student. The frame also contains, on a portion not exposed to view, the correct answer in parallel encoded form as a pattern of light and dark areas. In the system described, five areas are used to indicate one of up to 32 possible answers. The student selects an answer by actuating the appropriate key of a keyboard, the output of the keyboard being encoded as a parallel five-line signal. This signal is compared with another five-line signal obtained by optically sensing the frame areas to determine whether the selected answer is the correct answer. Systems such as this have the drawback that they are not adapted to simultaneous use by a number of students. Moreover, the paper band and associated mechanical and electrical components add to the overall cost.
Summers U.S. Pat. No. 3,848,082 shows an arrangement in which digital information such as a question is presented in serial form at a spot on the screen of an ordinary television receiver and is sensed by an optical transducer positioned adjacent to or remote from the receiver. The sensed information is decoded and presented as some form of visual readout. A digital code representing the correct answer may be transmitted again in serial form to the receiving equipment. A keyboard at the receiver permits the viewer to feed a coded representation of his answer into the system. A comparison of this coded representation with the coded representation of the correct answer can be used to provide an indication of the correctness of the answer. While this arrangement has the advantage of using an existing television receiver to communicate questions and answers, it still suffers the drawback that it is not readily adaptable to use by a number of students without substantial duplication of parts. Further, the serial transmission mode, which is primarily intended for such signals as news and weather reports having high data rates, is a relatively complicated and expensive mode to use for multiple-choice teaching systems having much lower data rates.